The present invention relates to a process for preparing a colorless and odorless rosin having an excellent thermal stability.
Heretofore, a rosin has been used as tackifiers for hot-melt adhesives and pressure-sensitive adhesives, modifiers for rubbers and plastics, raw materials for traffic paints, paper sizing agents, emulsifiers for synthetic rubbers, resins for inks, resins for paint, and the like. The rosin is colored in yellow or yellowish brown, impart its characteristic odor and has the defects that the rosin is poor in thermal stability and weatherability (hereinafter referred to thermal stability and weatherability as stability).
Accordingly, in order to prepare a colorless rosin having an improved stability which can be preferably used in an end product having improved qualities, a process for improving thermal stability of a rosin by disproportionating an unpurified rosin and a process for hydrogenating an unpurified rosin are employed. As a result, a disproportionated rosin and a hydrogenated rosin which are somewhat improved in stability are developed and are commercially available. However, the rosin sufficiently satisfied with color and stability has not yet been provided.
Japanese Examined Patent Publication No. 33771/1970 and Japanese Examined Patent Publication No. 20599/1974 disclose a method for disproportionating rosins with a specific organic sulfur compound. However, the disproportionated rosins do not have sufficient color and stability and impart odor.
As mentioned above, any conventional rosins, disproportionated rosins and hydrogenated rosins have not yet been satisfactory in odor, color and stability at a time. Accordingly, it has been desired that a rosin being colorless and odorless and having an excellent stability is developed in the field of art.
The object of the present invention is to develop a novel process for preparing a rosin having improved properties such as color, odor and stability in comparisonn with those of conventional rosins.
In the course of studying to solve the above-mentioned problems of the conventional rosins, it has been found that, all of the above-mentioned problems can be solved when a disproportionated rosin is used as a raw material and is subjected to purification and to hydrogenation in an optional order, and that the process is a very simple and novel process for producing a rosin having almost colorless, excellent properties such as odorless at heating and stability. The present invention is accomplished in accordance with the above novel knowledge.
These and other objects of the invention will become apparent from the description hereinafter.